This invention relates generally to cartons and more specifically to cartons formed from carton blanks for enclosing a plurality of containers, such as cans or bottles.
Various cartons in the packaging art enclose a plurality of containers, such as cylindrical cans or bottles, for packaging, shipping, displaying, and dispensing. Some of these cartons are constructed of fiber or paperboard, which is a cost-effective material.
During the packaging operation, the containers either are formed into groups and inserted into a carton sleeve made from a blank, or the group is placed on the interior surface of the carton blank and the blank is folded around the group to form the carton. The exterior surface of the carton typically has graphics or logos printed thereon. Sometimes the group of cans or bottles is soaked with water as it is placed into the carton. This can result either from the washing step, filling step or can result from the contents of the container being cold, which causes moisture to condense on the outside of the container. Additionally, known paperboard carton blanks have been laminated on the exterior or outer surface, such as for protecting the ink-based graphics, adding additional graphic layers, adding additional strength or waterproofing the carton. During the packaging operation in which the containers are placed on top of the flat carton blank, the carton blank that supports the container group is conveyed across, for example, rollers, through a continuous motion article packaging machine. As this happens, the containers, for example cans, sometimes spin in place within the article group. This spinning tends to wear the uncoated interior surface of the carton blank. Since the cans also can be wet, the moisture invades or soaks into the paperboard blank from the interior surface, and wicks toward the exterior surface where the graphics printing is located. The presence of moisture in these areas causes degradation not only of the graphics, but also to the carton itself.
Additionally, when containers with residual water or moisture are enclosed within the carton, a humid atmosphere is created. This humidity generally moistens the paperboard where it contacts the cans. After the wet cans or containers contact the substrate or paperboard, moisture wicks through the paperboard fibers to the clay-coated, print surface. In this situation, the wet printed-clay surface contacts conveyor belts and static rails as the package moves through the manufacturing process, such as through a fill line. This contact causes stress at the exterior surface of the carton, with the stress being greatest adjacent to where the cans within the carton contact the interior surface of the carton. At the high stress points, the clay coating can separate from the paperboard fiber, usually in small areas or spots. These places where the clay and/or fibers are removed creates a defect termed “water-induced abrasion”, which is also termed “ink picking” since the abrasion removes the ink or printing from the surface of the blank, sleeve, or carton. Ink picking can also occur where the water forms a bubble or bulge at the surface of the ink or graphics. This bubble then comes in contact with the conveyor belt or a static surface during the packaging process to create the ink picking and mar the graphics. Besides creating the problem of ink picking, which damages the appearance of the carton, the humidity can also mold or otherwise corrode the cans in the carton. Without protection, the wetness of the cans can cause a substantial enough amount of wearing that the outside surface of the container becomes structurally damaged, exhibits “can chime” (bulging areas of a can outline macroscopically apparent on the exterior surface of the carton), and/or experiences ink picking.
This visual defect of water based abrasion or ink picking typically occurs where the bottom portion of the cans contact the packaging substrate or paperboard. Uncoated or unlaminated paperboard or clay covered kraft paperboard often abrades when the wet or moisture laden containers are enclosed within a formed carton. Generally, lamination or other coating reduces or controls the impact of any moisture from the containers that could limit the structural integrity of, or damage ink or printing on, the carton. Conventional carton designs will often have an entire surface, typically the exterior surface, of the paperboard carton laminated. However, laminating entire surfaces of the carton is expensive.
Also, if the entire interior surface of the carton is coated and the end flaps are sealed with wet cans enclosed therein, a humid condition is created inside the carton. This humid condition can cause mold to develop on the cans and can develop corrosion on their surfaces.
As an alternative to laminating an entire surface of the carton, only the interior surfaces of the carton in contact with the upper and lower portions of the containers could be laminated. However, while coating the contact surfaces of the interior of the carton could prevent impact abrasion and/or ink picking proximate the surface contacts of the containers, the moisture in the interior of the carton from the containers merely could leak to the sides of the carton to create structural weakening of the uncoated paperboard at the sides.
Accordingly, a need exists for an abrasion resistant coating that addresses successfully the foregoing problems and shortcomings of the prior art. It is to the provision of such a coating that the present invention is primarily directed.